Tearable bottle caps comprising a top planar disk and an approximately cylindrical skirt depending from said planar disk to snugly fit around the neck of the bottle and having a pull tab and a score line starting from the lower edge of said skirt in order to enable the tearing of said tab along said score line so as to loosen the cap from the bottle neck, have been known for long.
For instance, British patent specification No. 816,787 published July 11, 1959 discloses a bottle cap having a pull tab and a slant core line starting from the lower end of the skirt and extending up to the portion of the skirt that is provided with an internal bead being used to be snapped over a circumferential flute provided near the upper edge of the bottle neck, which upper edge is sealed by a plurality of circumferential ribs provided on the inner surface of the top disk of the cap. This cap, however, while providing the principle of opening the cap by means of a pull tab and a score line slanting from the bottom of the cap and up to the bead portion thereof, is deficient in that it relies, for the sealing engagement of the cap with the bottle neck, merely on the provision of said internal bead and the provision of said circumferential ribs that supposedly should seal on the upper edge of the bottle neck, but this arrangement is not quite efficient, because it is necessary to provide the flute on the neck of the bottle in a very accurate position in order to enable sealing of the bottle neck against the circumferential ribs of the top disk of the cap. On the other hand, and while said ribs may be sealingly engaged against new bottles, it is quite clear that, when the bottles are spoiled in use, the sealing engagement would also be materially useless and, therefore, this type of caps is not adequate for bottles of the type which are interchanged or refilled for marketing purposes.
Another tearable cap for bottle necks is also disclosed in U.S. Pat. No. 3,032,226 to Terwilliger, patented May 1, 1962. This cap for the first time provides for a vertically extending pull tab and a vertical score line to tear the cap, but again relies on the provision of an internal bead provided at the lower edge of the skirt of the cap and effects the sealing engagement with the bottle neck by means of the provision of a channel-like section which comprises an inner circumferential flange which is engaged within the top of the flask, whereby this engagement mainly relies on the force exerted by the inner cylindrical flange on the inner surface of the wall of the bottle neck, which cannot be very strong unless the contents of the flask are under pressure. This cap, therefore, is not useful for common type large capacity bottles and, on the other hand, the vertical score line provided therein is also very inefficient to tear the cap, with the consequent disadvantages caused thereby. Also, the manufacture of a cap of the characteristics disclosed by Terwilliger is extremely difficult, particularly considering the modern methods of injection molding of this type of caps.
One other tearable cap for bottle necks is described and shown in U.S. Pat. No. 3,120,900 to Faulstich, patented Feb. 11, 1964, which is a combination of the above mentioned patents, in that it provides a vertically extending pull tab as in U.S. Pat. No. 3,032,226 and a slant score line as in British specification No. 816,787, but also provides a score line which extends throughout the circumference of the cap, so that the tearing of said cup may be complete around the circumference thereof. The sealing engagement of this cap, however, leaves much to desire because it relies on an accurately placed dovetail engagement between the cap and the bottle neck, whereby this type of cap is more adequate for plastic containers and is quite unsuitable for rigid containers, regardless of the fact that the sealing engagement is also provided by an internal circumferential bead provided on the skirt of the cap. While said bead efficiently holds either the corresponding groove of the plastic container or the corresponding bead of the bottle neck, the latter, that is, said groove or said bead of the bottle neck must be provided at accurate positions, because the sealing engagement is made between the upper edge of the container and the inner surface of the top disk of the cap, which is not quite efficient for large capacity bottles or for large diameter bottle necks.
One other tearable cap is shown and described in U.S. Pat. No. 3,392,860 to Faulstich, patented July 16, 1968, which also contains a vertically extending pull tab and a diagonal or slanting score line continued by a small circumferential score line, but the sealing engagement of this cap relies on the provision of an inner cylindrical flange which engages the inner surface of the bottle neck and said sealing engagement also relies on an outwardly directed or external hollow bead which is an arcuate portion provided at a predetermined position around the skirt of the cap, in order to insert within said hollow bead, the upper bead of the bottle neck. The external form of the cap, that is, the arcuate portion of the external bead provided on the skirt of the cap, renders series manufacture of said cap considerably difficult and also renders the sealing engagement relatively disengageable, because the arcuate thin portion of the skirt which provides the external bead of the cap of U.S. Pat. No. 3,392,860 does not provide a sufficiently strong engagement to maintain the cap permanently in its closed position, whereby said sealing engagement may be lost through misuse or other external causes, thus providing a rather unsafe cap for bottle necks, particularly if the bottles are of a large capacity or contain large diameter bottle necks.
Another embodiment of a tearable cap for a bottle neck is disclosed in U.S. Pat. No. 3,338,446 to Faulstich, patented Aug. 29, 1967, which is an improvement of the cap disclosed in U.S. Pat. No. 3,120,900 also to Faulstich, and which incorporates, as additional elements, a vertical pull tab having a short vertical score line followed by a slant score line and thereafter by a circumferential score line to tear the cap throughout the circumference, and said cap having rigidifying gussets for avoiding deformation of the cap and at the same time facilitating opening of the flask, and providing reclosure devices. This cap, however, again relies, for tight closure engagement, on the provision of internal accurately positioned beads, which are introduced in also accurately positioned grooves provided on the outer surface of the bottle neck, and complemented by an inner cylindrical flange which snugly fits the internal surface of the bottle neck, whereby both the manufacture of the tearable cap and the manufacture of the bottle neck must be of special characteristics and is rendered extremely difficult, in view of the fact that accurately positioning of the grooves and the beads is required.
Another tearable bottle cap is shown and described in U.S. Pat. No. 3,392,862 also to Faulstich, patented July 16, 1968, wherein said bottle cap is provided with a vertically extending pull tab which tears a vertical score line continued by a short slant score line followed by a partially circumferential slant line, but this bottle cap relies, for its sealing engagement with the bottle neck, on the provision of the above mentioned external hollow bead to insert the upper bead of the bottle neck thereinto, and rigidifying elements are provided on the top disk of the cap in order to avoid undue deflection thereof inwardly or outwardly of the bottom, so as to improve the safety of the sealing engagement of the hollow internal bead against the upper bead of a bottle neck, particularly of the high capacity type flasks. The defects of this tearable bottle cap, however, are the same as those described in connection with the bottle cap of U.S. Pat. No. 3,392,860, with the only exception that the sealing engagement of the external bead with the upper bead of the bottle neck is somewhat improved by the provision of the rigidifying elements of the top disk of the cap.
One other design of a tearable bottle cap is disclosed in U.S. Pat. No. 3,840,137 also to Faulstich, patented Oct. 8, 1974, which provides the same type of outer hollow bead to engage the upper bead of the bottle neck but which, for the first time, provides a bottle cap which may be used both with screw threaded or unthreaded neck bottles, by furnishing a sealing engagement which does not rely on the snug fit between the inner wall of the hollow bead and the upper bead of the bottle neck, but which relies on the provision of a plurality of circumferential ribs on the lower portion of the bead of the cap, in order to snugly fit around the bottle thus providing a sealing engagement which may be regarded as more secure. While this type of bottle cap may be ideally used for threaded neck bottles, because the top disk of the cap fits on the upper edge of the bottle neck, thus providing almost absolute stability of the bottle cap, the defect of having the top disk of the bottle cap directly seating in sealing engagement against the upper edge of the bottle neck, is very likely to produce breakage of said bottle neck when piling of the bottles one over the other is contemplated, as well as frequent breakage of the bottoms of the upper bottles piled, in view of the shocks received by careless handling. On the other hand, when this type of cap is used with unthreaded neck bottles, then there is a cushion left over the upper edge of the bottle neck, which suppossedly acts as a shock absorber which may avoid the above disadvantage, but the problem with this bottle cap is that, when the bottles are piled one over the other, the pressure exerted on the top disk of the cap may be sufficiently strong to flatten the top cushion and to dislocate the sealing engagement between the lower ribs of the outer bead of the cap and the upper bead of the bottle neck, thus defeating the purpose of the cap.
U.S. Pat. No. 3,979,002 also to Faulstich, and patented Sept. 7, 1976 discloses an improvement over the cap shown and described in U.S. Pat. No. 3,392,860, and also more particularly refers to an improvement to the bottle cap of U.S. Pat. No. 3,840,137, in that it is also suitable for serving to close both threaded and unthreaded neck bottles, but providing the sealing rib on the upper third portion of the external bead, which clearly is not the solution to the dislocation of the sealing engagement when the caps are used for unthreaded neck bottles and the bottles are piled and thus exert a pressure on the top disk of the cap of the bottle below, which tends to dislocate the sealing engagement thereof. Also, the bottle cap of U.S. Pat. No. 3,979,002, when used with threaded neck bottles, while perfectly sealing the said bottle, is also likely to produce breakage in view of the fact that it does not provide any cushion which may serve as a shock absorber against breakage of the upper edge of the bottle neck or of the bottom of the bottles piled above.
From the above, it may be concluded that, while the provision of an outer hollow bead on a bottle neck may be of relatively economical construction because it involves the use of less material than an internal solid bead, said external beads do not provide a completely safe sealing engagement, particularly when the bottle caps are to be suitable for use with both threaded and unthreaded neck bottles and particularly when, as is common in handling the bottles, they are piled one over the other with the consequent risks of breakage of the bottles when they are threaded neck bottles or of dislocation of the sealing engagement when they are unthreaded neck bottles.
However, while the solid inner beads provide for a better sealing engagement than the outer hollow bead, it has been very well known that, for the provision of an inner bead, it is mandatory to provide a complementary groove on the bottle neck, accurately positioned thereon in order to receive the inner bead of the bottle neck, and it is also mandatory to provide either sealing circumferential ribs on the top disk of the bottle, or a pressure fit between the inner surface of said top disk of the bottle cap and the upper edge of the bottle. This, obviously, rendered it impractical to use a bottle cap provided with an internal bead, both with threaded and unthreaded neck bottles.
Finally, U.S. Pat. No. 4,303,167 to Francisco P. Martinez, patented Dec. 1st, 1981, describes a bottle cap which, being provided with the advantages of having the sealing characteristics of an internal solid bead, is also capable of being useful both for threaded or unthreaded neck bottles, and provides for a cushion to avoid breakage of the necks or of the bottoms of piled bottles, which up to the present date has been provided only by the unsafe outer hollow beads disclosed in the above mentioned patents to Faulstich. According to Martinez, the above action is carried out by the provision of a solid inner bead for being engaged with the lower portion of the upper bead of the bottle neck, and a plurality of inwardly radially directed projections in the skirt, which extends from the upper disk down to such a position that their lower ends serve as stops for the upper portion of the upper bead of the bottle neck, thus accomplishing a full-proof closure, as well as a rigid skirt which will not tend to be deformed when the bottles are piled.
While the cap of the above identified U.S. Pat. No. 4,303,167 practically solves all the problems of the caps of the prior art, said cap shows the drawbacks that occasionally, for instance, when several bottles are piled one above the other or when an undue pressure is exerted on the upper disk of the cap, it suffers a slight side distorsion of the projections, whereby the hermeticity of the cap may be destroyed when the inner bead is separated from the lower part of the upper bead of the bottle neck. Therefore, with this type of caps of U.S. Pat. No. 4,303,167, it has been recommended not to pile a large number of bottles, since otherwise the resistance of the projections may be exceeded and the hermiticity of the cap may be destroyed to a certain extent.